1. Field of the Invention
The present invention relates to a thione derivative or a non-toxic salt thereof which is effective in reduce inflammation, pain, or fever, a method for preparing the same, and a pharmaceutical composition containing the same as an active ingredient.
2. Description of the Related Art
Most nonsteroidal antiinflammatory agents are responsible for blocking enzyme, cyclooxygenase (COX) or prostaglandin G/H synthase, to reduce inflammation, pain, or fever. In addition, they inhibit uterus contraction caused by hormones and also inhibit growth of several cancers. Cyclooxygenase-1 (COX-1) was first discovered in bovine. The COX-1 is constitutively expressed in a variety of cell types. Unlike the COX-1, cyclooxygenase-2 (COX-2) is a recently discovered isoform of cyclooxygenase that can be easily induced by mitogen, endotoxin, hormone, growth factor, or cytokine.
Prostaglandin is a potent mediator for various pathological and physiological processes. The COX-1 plays important physiological roles such as in the release of endogenous prostaglandin, the maintenance of the shape and the function of stomach, and the blood circulation in the kidney. On the other hand, the COX-2 is induced by an inflammatory factor, hormone, a growth factor, or cytokine. Therefore, the COX-2 is involved in pathological processes of prostaglandin, unlike the constitutive COX-1. In this regard, selective inhibitors of the COX-2 produce fewer and less side effects in terms of action mechanism in comparison with conventional nonsteroidal antiinflammatory agents. In addition, they reduce inflammation, pain, and fever and inhibit uterus contraction caused by hormones and growth of several cancers. In particular, they are effective in decreasing side effects such as stomach toxicity and kidney toxicity. Still furthermore, they inhibit the synthesis of contractile prostanoid, thereby leading to suppression of the contraction of smooth muscles. Therefore, they help in preventing premature birth, menstrual irregularity, asthma, and eosinophilic disease.
In addition, it is anticipated that selective inhibitors of the COX-2 would be effective in treating osteoporosis and glaucoma. Utility of selective inhibitors of the COX-2 is well described in publications [John Vane, “Towards a Better Aspirin” in Nature, Vol. 367, pp 215-216, 1994; Bruno Battistini, Regina Botting and Y. S. Bakhle, “COX-1 and COX-2: Toward the Development of More Selective NSAIDs” in Drug News and Perspectives, Vol. 7, pp 501-512, 1994; Urology, Vol. 58, pp 127, 2001; David B. Reitz and Karen Seibert, “Selective Cyclooxygenase Inhibitors” in Annual Reports in Medicinal Chemistry, James A. Bristol, Editor, Vol. 30, pp 179-188, 1995].
Various selective COX-2 inhibitors having different structures are known. Among them, a selective COX-2 inhibitor having a diaryl heterocyclic structure, i.e. a tricyclic structure has been widely studied as a potent candidate. The diaryl heterocyclic structure has a central ring and a sulfonamide or methylsulfone group attached to one of the aryl rings.
One selective COX-2 inhibitor, Celecoxib of formula 87 is disclosed in U.S. Pat. No. 5,466,823. The Celecoxib is a substituted pyrazolyl benzenesulfonamide derivative.

Another selective COX-2 inhibitor, Rofecoxib of formula 88 is disclosed in WO 95/00501. The Rofecoxib has a diaryl heterocyclic structure with a central furanone ring.

Valdecoxib of formula 89 as another selective COX-2 inhibitor is disclosed in U.S. Pat. No. 5,633,272. The Valdecoxib has a phenylsulfonamide moiety with a central isoxazole ring.

The selective COX-2 inhibitors of formulas 87 to 89 are effective inflammatory therapeutic agents with fewer and less side effects in comparison with conventional nonsteroidal antiinflammatory agents.